The present invention relates to a door for a motor vehicle and in particular an agricultural vehicle, such as a tractor, where it is desirable to maximize visibility.
It is known from U.S. Pat. No. 6,247,746 to provide a door for a tractor which comprises a frameless single pane of transparent material pivoted at one edge on a pillar of the motor vehicle. This door is mounted on the pillar by means of a pair of hinges affixed to the pane. To achieve the necessary rigidity, the hinges are connected to one another by a reinforcing member that extends generally parallel to the pivot axis and interconnects the wings of the hinges that are affixed to the pane.
In the door of the ""746 patent, the reinforcing member extending between the hinges obstructs the driver""s view and, thus, presents a problem with respect to maximizing the visibility of the operator through the door. Accordingly, an improved door for the operator""s cab of an agricultural tractor would be desirable to mitigate this problem.
It is therefore an object of the present invention to provide a door for the operator""s cab of an agricultural tractor that would maximize visibility for the operator.
Thus, in accordance with a first aspect of the invention, there is provided a door for a motor vehicle comprising a frameless single pane of transparent material pivoted at one edge on a pillar of the motor vehicle, wherein the pivot includes a reinforcing member extending generally parallel to the pivot axis, which reinforcing member is arranged in line with the pillar on which the door is mounted when viewed from the position of the driver of the vehicle, so as to minimize obstruction of the field of view of the driver.
The pivot may conveniently comprise two hinges having wings connected to the transparent pane, the reinforcing member extending between the latter two wings.
The invention recognizes in its first aspect that the driver""s field of view is unavoidably obstructed by the pillar on which the door is mounted. By aligning the pillar with the hinge reinforcing member, the invention allows the hinges to be reinforced without further obstructing the driver""s field of view.
Though the door depicted in U.S. Pat. No. 6,247,746 may be regarded as frameless in that that there is no frame that fits around the entire glass pane, the door nevertheless requires the use of long support arms which are connected to the hinge members and to which the glass pane is affixed near its front and rear edges. These support arms, which are required for rigidity, themselves obstruct the driver""s field of view.
According to a second aspect of the invention, there is provided a door for a motor vehicle comprising a frameless single pane of transparent material pivoted at one edge on a pillar of the motor vehicle, wherein the pivot comprises two hinges affixed to the pane and a reinforcing member extending generally parallel to the pivot axis and interconnecting the wings of the hinges that are affixed to the pane, characterized in that the wings of the hinges have surfaces that mate with the transparent pane, which surfaces are machined after the wings have been permanently connected to one another by the reinforcing member.
By forming contoured mating surfaces on the hinge wings that mate accurately with the surface of the transparent pane, the second aspect of the invention allows the pane to be held rigidly by only two fixings that connect directly to the hinge wings. This avoids the need for any further support aims to steady the door when it is open, thereby maintaining the driver""s field of view clear.
It is preferred that the hinges and the reinforcing member be cast in one piece but it is alternatively possible for them to be formed from separate components that are suitably permanently connected to one another, such as by welding.
It is important in the second aspect of the invention that the hinges and the reinforcing member should not be able to move relative to one another after the mating surfaces of the hinges have been machined to match the contour of the transparent pane.
In a preferred embodiment of the invention, the pane is contoured such that the pane is in tension when the edges of the pane seal against the door opening, the tension in the pane serving to improve the seal between the pane and the door opening. In other words, in its relaxed state, the pane has a greater curvature than the door opening and the pane is flattened when the door is closed and is held in tension by the door latch mechanism.
Conveniently, the contour of the pane in its relaxed state conforms to that of the door opening in the vicinity of the pivot axis of the hinges and in the vicinity of the door latch mechanism, the deformation of the pane to conform to the door opening being at a maximum along a line transverse to the imaginary shortest line from the latch to the pivot axis. Thus the pane is held against the door opening to form a seal along one direction by the action of the latching mechanism and, transverse to this direction, the tension in the pane resulting from its deformation away from its relaxed position is relied upon to effect a seal against the door opening.
As is conventional, a rubber sealing strip may be provided around the perimeter of the door opening, or more preferably along the periphery of the transparent pane to effect a weatherproof seal.
To assist in closing the door, it is preferred to provide a pull handle, that it is attached at one end to the lower hinge wing and is connected to the transparent pane at its other end.
The pull handle may also conveniently be connected to the latching mechanism. Additionally, the pull handle may be connected to the vehicle frame by a pivoting arm that acts as a stop to limit the extent to which the door can be opened. The latter arm may if desired include a damper to resist the opening of the door in case the pane is caught by a gust of wind when the door is partially open.
For clarity and durability, it is advantageous for the transparent pane to be formed of glass, preferably laminated for safety, but it is alternatively possible to use a plastics material, such as a polycarbonate.
These and other objects, features and advantages are accomplished according to the instant invention by providing a door for the operator""s cab on an agricultural tractor which is formed from a frameless single pane of transparent material pivoted at one edge on a pillar of the tractor. The pivot is formed of two hinges affixed to the pane and a reinforcing member extending generally parallel to the pivot axis and interconnecting the wings of the hinges that are affixed to the pane. The reinforcing member is arranged in line with the pillar on which the door is mounted, when viewed from the position of the driver of the vehicle, so as to minimize obstruction of the field of view of the driver. In another aspect of the invention, the surfaces on the hinges that mate with the pane are machined to match the contours of the pane while the reinforcing member and the hinges are in one piece.